The invention relates to a shock absorber for damping courses of motion of a vehicle as defined herein. A shock absorber has been set forth by which the damping force is variable by means of an electromagnetic valve assembly. The valve assembly is disposed on the damper piston. It includes a magnet coil, an armature and a control slide connected to the armature; the position of the control slide determines the throttling of the pressure fluid flowing back and forth between the two work chambers.
Relative major forces are necessary to actuate the control slide. These forces have to be generated by the magnet coil. This means that a large, heavy, unfavorably expensive magnet coil must be provided. Because of the major forces, short switching times, which are often desired and necessary, are presumably not always attainable.
In the heretofore set forth device the force of the magnet coil determines the position of the control slide, and this position in turn determines a size of throttle cross section. In a shock absorber with a variable throttle cross section, however, what is primarily sought is not so much to control the size of the throttle cross section, but rather to control the damping force and hence the damping of courses of motion, which is directly dependent on a differential pressure between the two work chambers. If the throttle cross section is controlled, then the damping force is dependent not only on the throttle cross section but also on a relative speed between the damper piston and the cylinder, and on the viscosity of the pressure fluid, for example, among other factors. The viscosity can fluctuate relatively markedly, for instance as a function of temperature.
The valve assembly in the known structure is disposed on the damper piston. Other shock absorbers are known, however, in which a valve assembly is provided outside the cylinder.